1. Field of the Invention
The invention concerns a medical device having at least one transducer fashioned for generation of high-intensity focused ultrasound (HIFU), and with a magnetic resonance (MR) apparatus for generation of magnetic resonance exposures for a temperature monitoring as well as a corresponding transducer and a method for generation of magnetic resonance exposures for temperature monitoring of a region irradiated with high-intensity focused ultrasound.
2. Description of the Prior Art
High-intensity focused ultrasound (HIFU) is used in medicine, for example for tumor treatment. It is important to implement an accompanying temperature observation or monitoring in order to know whether the generated temperature is sufficient in order to destroy the tumor tissue and in order to ensure that the surrounding tissue is not affected by temperatures that are too high that may possibly cause permanent damage.
Conventionally, a temperature monitoring with the use of magnetic resonance phase images is implemented for such temperature monitoring. The temperature monitoring by magnetic resonance tomography is based on, for example, the proton resonance frequency shift that occurs when hydrogen bonds in water are attenuated due to thermal energy. It is problematic that this effect is relatively weak, such that phase difference images must be produced before and after the heating of the tissue. These images are subsequently subtracted to correct the effect.
Due to susceptibility changes that result, for example, in the environment of the image exposure region because the transducer for the generation of the high-intensity focused ultrasound used for treatment is filled with air, errors in the temperature measurement are caused when the transducer has moved in the time between acquisition of a reference image and a “temperature image”.
It has been typical to either re-acquire a reference image for each new position of the transducer for generation of the ultrasound (which transducer is moved through a water bath arranged below the patient) in order to allow for the new susceptibility conditions, or to use an array of a number of transducers with which the focus can be varied without a position change of the array.
The acquisition of new reference images for each transducer position is comparably time-consuming and extends the duration of treatment of the patient. Moreover, the transducer arrays require a significant structural expenditure and have considerable manufacturing costs associated therewith.